(1) Investigations on the interaction of enzymes with lipid substrates will continue using three types of dispersion of a complex lipid, such as sphingomyelin: a. mixed micelles of lipid and detergent. b. substrate in a liposomal structure. c. substrate spread as a monolayer at an air-water interface. The influence of the physical state of the substrate on the rate of enzymic hydrolysis will be analyzed. (2) Work will also be continued on lysolecithinase of brain and other tissues. The nature of the inhibitory effect of micellar lysolecithin will be further analyzed. (3) Kinetic aspects of sphingomyelin hydrolysis by sphingomyelinase of post-mortem tissues of normals and of patients with Niemann-Pick's disease will be compared. (4) Lipases of rat brain will be characterized, special attention being paid to monoglyceride lipase. (5) Sublysosomal particles will be analyzed as to their enzymic consistency. The existence of a multi- enzyme complex of sphingolipid hydrolases will be tested.